The present invention relates to digital rights management.
A digital object is a collection of digital data. Data in a digital object can represent content, such as text, video, music, computer instructions and other work, that is subject to limited use or distribution, e.g., protected legally by intellectual property (“IP”) rights, such as copyright. For example, an electronic representation of a book (i.e., an e-book), a moving picture, or a sound record has typically content protected by copyright. Alternatively, a content owner may wish to protect content in a digital object without pursuing legal protection.
When digital objects are distributed, e.g., sold or lent to consumers, content can be protected by a digital rights management (“DRM”) system. A DRM system defines and enforces digital rights. A digital right is a permission to perform one or more actions that involve a digital object including protected content. By managing digital rights, the DRM system allows content owners, on one hand, to prevent unauthorized use or distribution of the protected content and, on the other hand, to selectively authorize users to perform actions that involve the protected content.
In a typical DRM system, a digital object with protected content is associated with a set of digital rights, where each digital right specifies one or more actions that can be authorized using the right. For example, a digital document can be associated with a set of digital rights including a print right and a display right that can be used to authorize printing and displaying, respectively. Optionally, the set of digital rights can specify conditions on one or more rights in the set. A condition on a right specifies restrictions for performing an action specified by the right. For example, conditions on the print right can specify a limited time period, a portion of the content, or a maximum number of pages for printing the document. Digital rights and corresponding conditions can be expressed using, e.g., rights languages such as eXtensible rights Markup Language (“XrML”) or Open Digital Rights Language (“ODRL”).
For authorizing an action that involves the digital object, the DRM system can include a DRM engine. The DRM engine processes digital rights and provides authorization for actions involving protected content based on the digital rights. For example upon request, the DRM engine can evaluate a set of digital rights associated with a digital object, and based on the evaluation, provide or deny authorization for an action involving the digital object.
Traditionally, in order to minimize unauthorized manipulation of digital rights, once a set of digital rights is associated with a digital object, the associated set of digital rights can be modified only by an owner of the protected content. For example, if a consumer buys a digital object with a set of initial rights and later requests additional rights, the content owner provides a new set of digital rights that includes both the initial rights and the additional rights.